The development of a neuron is influenced by specific cues that it obtains from interactions with other cells and from its environment. These cues cause the neuron to express morphological and biophysical characteristics that ultimately determine the function of the mature neuron in its network. Recent studies of the physiological, morphological, and neurochemical development of the moth's antennal lobe (the primary olfactory center in the brain) have implicated several hormonal and cellular interactions as critical for the normal development. The proposed study will take advantage of the controlled environment of tissue culture to test directly the importance of interactions among sensory axons, antennal-lobe (AL) neurons and glial cells as well as hormonal influences on the morphological and biophysical development of the neurons. Co-culture procedures will be used to examine the effects of afferent axons on the development of neuritic arbors and voltage- and ligand-gated channels of AL neurons. In addition, the effects of the steroid hormone 20-hydroxyecdysone (20-HE) and the monoamine 5-hydroxytryptamine (5-HY or serotonin) on the development of AL neurons and glial cells will be studied. The hypothesis that glial cells act as intermediaries in the passage of inductive signals between antennal sensory neurons and AL neurons will be tested specifically. The proposed studies will give insights into direct intercellular influences on development and will lay the groundwork for future studies of the molecular mechanisms underlying these interactions.